The present invention relates generally to medical methods and devices, and more particularly, to methods and devices for cooling and perfusing the spinal vasculature of a patient during thoracoabdominal aortic surgery.
Approximately 50,000 patients undergo surgical procedures on the aorta each year for the treatment of various conditions, such as aortic aneurysms, occlusional diseases and aortic dissection. An exemplary procedure includes conventional aortic grafting, which involves clamping the aorta upstream from the damaged region to prevent blood loss at the surgical site, excising a cylindrical portion of the aorta encompassing the damaged region, and replacing the removed portion of the aorta with a graft. During this procedure, the intercostal arteries leading to the damaged region of the aorta are individually severed from the aorta.
The cessation of blood flow through the aorta causes spinal ischemia in about 10-15% of patients, due to the reduction or cessation of oxygenated blood within the spinal vasculature that would normally be supplied thereto by the intercostal arteries downstream from the clamped portion of the aorta. Because spinal ischemia can quickly lead to irreversible spinal tissue damage, a minimal amount of time is allowed to suture the intercostal arteries onto the graft. Often, when the intercostal arteries are severed from the aorta, none or very few of them are sutured onto the graft due to the time limitations. The aortic clamp is removed after the graft is attached, thereby supplying oxygenated blood to the spinal vasculature via the unsevered intercostal arteries, albeit in a non-robust manner. Spinal neurological damage is directly related to cross-clamp time and the number of severed intercostal arteries.
To ease reattachment to the graft, the intercostal arteries are sometimes integrally severed from the aorta, i.e., patches of the posterior wall of the aorta are excised, each of which carries several intercostal arteries. After the aorta has been grafted, the aortic patch can be sutured onto the graft, minimizing the amount of time it takes to connect the intercostal arteries to the aorta. Regardless of whether the intercostal arteries are individually or integrally severed from the aorta, however, there remains danger of causing irreversible damage to the spinal tissue resulting from ischemia.
For these reasons, it would be desirable to provide improved methods and assemblies for preventing spinal ischemia during the performance of surgical procedures on the aorta, and allowing more time to restore a robust blood flow within the spinal vasculature.
The invention provides single or multiple vessel perfusion assemblies and methods for selectively treating the spinal vasculature of a patient during thoracoabdominal surgery.
Methods performed in accordance with the present invention comprise perfusing the spinal vasculature with a medium by flowing a medium into the open ends of one or more intercostal arteries. The intercostal arteries can be accessed by individually or integrally severing the intercostal arteries from the aorta, or alternatively, the intercostal arteries can be accessed through a puncture or slit within the wall of the aorta. Preferably the medium is cooled to induce hypothermia within the spinal vasculature without cooling the rest of the body (selective spinal hypothermia). The cooled medium can be composed of a biocompatible liquid, such as, e.g., a saline solution, that is flowed from an external source and is cooled. Alternatively, the cooled medium can be composed of oxygenated blood that is shunted from a oxygenated blood filled cavity, such as the heart or proximal aorta upstream from the intercostal arteries and cooled. The characteristics of the cooled medium, such as, e.g., the temperature, flow rate and pressure of the medium is preferably controlled to maintain a viable environment for the spinal vasculature. The methods of the present invention can be performed by employing any vessel perfusion assembly, but are preferably performed by flowing a medium into the plurality of intercostal arteries, which can be facilitated by employing single and multiple vessel perfusion assemblies, such as those described herein.
Multiple vessel perfusion assemblies constructed in accordance with the present invention provide a means for simultaneously flowing a medium into the open ends of a plurality of vessels. In a first embodiment, the multiple vessel perfusion assembly includes a branched conduit having a common portion, an inflow cannula formed at one end of the common portion and a plurality of outflow cannulae respectively formed at the other end of the common portion. The branched conduit includes a lumen for conveyance of a medium therethrough. The inflow cannula can comprise any tubular member configured to be inserted through the wall of the heart or proximal aorta, and the outflow cannulae can comprise any tubular members configured to be inserted into the open ends of vessels. The inflow cannula includes an inlet, and the outflow cannulae include outlets, which are in fluid communication with the lumen of the branched conduit. In this manner, insertion of the inflow cannula through the heart or aortic wall and respective insertion of the plurality of outflow cannulae into the open ends of the vessels provides flow of oxygenated blood from the heart or aorta into the vessels. The branched multiple vessel perfusion assembly further includes a cooler for cooling the medium as it passes through the lumen of the branched conduit.
In a second embodiment, the multiple vessel perfusion assembly includes a conduit, an inflow cannula formed at one end of the conduit, and a perfusion chamber formed at the other end of the conduit. The conduit includes a lumen, and the inflow cannula and perfusion chamber respectively include an inlet and a substantially enclosed cavity, which are in fluid communication with the lumen of the conduit. The perfusion chamber includes vessel engaging outlets, which are configured to securely receive the open ends of a plurality of integrally severed vessels (an aortic patch). In this manner, insertion of the inflow cannula through the heart or proximal aortic wall, and disposition of the open ends of the severed vessels into the vessel engaging outlets provides simultaneous flow of oxygenated blood from the heart or aorta into the vessel inlets contained within the aortic patch.
A single vessel perfusion assembly constructed in accordance with the present invention provides a means for flowing a medium into the open end of a vessel. In an embodiment, the single vessel perfusion assembly includes a conduit, an inflow cannula formed at one end of the conduit and an outflow cannula formed at the other end of the conduit. The conduit includes a lumen for conveyance of a medium therethrough. The inflow cannula includes an inlet, and the outflow cannula includes an outlet, which are in fluid communication with the lumen of the conduit. In this manner, insertion of the inflow cannula through the heart or aortic wall and insertion of the outflow cannula into the open end of the vessel provides flow of oxygenated blood from the heart or aorta into the vessel.
Alternatively, the above multiple vessel perfusion assemblies can forego the employment of an inflow cannula. In this case, a medium, such as, e.g., a saline solution, can be suitably introduced into the conduit of the multiple vessel perfusion assemblies. Preferably, the multiple vessel perfusion assemblies further include control devices for conditioning the medium to maintain a viable environment for the tissue to which the vessels lead. For instance, a cooler and associated thermostat can be used to cool and control the temperature of the medium. A pump and associated manometers can be used to control the flow rate and pressure of the medium.
Other and further objects, features, aspects, and advantages of the present invention will become better understood with the following detailed description of the accompanying drawings.